The application of paint to the body of a vehicle is a sensitive process. The quality, durability and color matching of the paint are critical in producing a high quality product, and therefore require significant quality control efforts.
Generally, paint film thickness is monitored by the use of hand-held thickness sensors, such as an ultrasonic pulse echo thickness meter, or a magnetic induction meter. These sensors are handled by an operator who must manually apply the sensor against the surface of the vehicle in a position normal to the surface at a plurality of locations on the surface. In the performance of this measurement, it is highly important that the operator position the sensor normal to the particular location being sensed, and it is also critical that the operator position the sensor consistently at the same plurality of locations on the surface being sensed. Errors in the angle of the sensor relative to the surface or in the location of the sensor on the surface can adversely effect quality control. Because a significant reliance is placed upon the operator, a significant amount of error is introduced in the quality control process.
Another problem with the use of a hand-held sensor is that the sensor must be sequentially moved from location to location on the product being inspected to obtain a complete set of measurements. This movement of the sensor from location to location can be very time consuming, and therefore expensive.
It is therefore desirable to provide a method and apparatus for accurately and repeatably positioning a sensor at a plurality of locations on a vehicle surface for measuring paint film thickness, or other surface characteristics, at the particular locations without requiring operator handling.